Opicapone Shows No Superiority Over Placebo for Fluctuation-Related Pain in Phase 4 Parkinson Trial

Findings from the phase 4 OCEAN trial (NCT04986982), recently published in Movement Disorders, showed that opicapone (Ongentys; Amneal Pharmaceuticals), a third-generation catechol-O-methyltransferase (COMT) inhibitor approved for Parkinson disease (PD), was not superior to placebo for reducing fluctuation-related pain among patients with PD.¹

These findings matter clinically because pain affects an estimated 68% to 95% of patients with PD,² yet remains difficult to treat pharmacologically. Conducted by lead author Kallol Ray Chaudhuri DSc, FRCP, MD, director of Research and Clinical Trials at Kings College Hospital, London Dubai, OCEAN is the latest in a series of placebo-controlled trials to fall short on this end point despite growing recognition of its burden.

Study Overview

OCEAN was a randomized, double-blind, placebo-controlled, parallel-group trial conducted at sites in the UK, Portugal, Italy, France, Spain, and Germany. Investigators enrolled patients with idiopathic PD (modified Hoehn and Yahr stages 1–3 ON) experiencing end-of-dose wearing-off on 3 to 8 daily doses of levodopa/dopa decarboxylase inhibitor therapy, plus pain defined by a King's Parkinson's Disease Pain Scale (KPPS) domain 3 score of at least 12.

Patients were randomized 1:1 to opicapone 50 mg once daily or placebo for 24 weeks, with paracetamol or tramadol allowed as rescue medication. Of 144 patients enrolled, 122 comprised the full analysis set (opicapone, n = 59; placebo, n =6 3). The primary end point was change from baseline to week 24 in KPPS domain 3; secondary end points included total KPPS score, MDS-NMS total score, off time, and rescue medication use.

Key Findings

Both arms improved substantially. KPPS domain 3 scores fell 8.8 points (SD, 6.9) with opicapone versus 9.3 points (SD, 6.2) with placebo, a nonsignificant difference of 0.30 point (95% CI, −1.96 to 2.55; P = .7940). KPPS total score fell 18.1 points versus 16.1 points (P = .7538), and MDS-NMS total score fell 28.4 versus 27.1 points (P = .9391), both favoring opicapone numerically but not statistically. Notably, opicapone's KPPS total score improvement exceeded the established 3-point minimum clinically important difference, even without between-group significance.

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The opicapone group used tramadol fewer days (15.8 vs 44.5) and fewer daily capsules than placebo, though paracetamol use was similar. Reduction in off time (95.1 vs 71.0 minutes) also favored opicapone without reaching significance. Safety was consistent with opicapone's known profile, with treatment-emergent adverse events occurred in 62.5% versus 57.1% of patients, with nausea most common in both arms; no deaths occurred.

Clinical Context and Interpretation

Pain remains one of the most common yet undertreated nonmotor symptoms of PD, spanning musculoskeletal, dystonic, radicular, central, and fluctuation-related subtypes.² Prior placebo-controlled trials of dopaminergic and non-dopaminergic agents, including prolonged-release oxycodone-naloxone and duloxetine,^4,5 have similarly failed to separate from placebo on pain end points. Opicapone itself carries established efficacy for reducing off time in earlier pivotal trials,³ and OCEAN is described by its authors as the first randomized trial to use KPPS domain 3 as a primary end point.

The authors attributed the negative primary finding largely to an unusually large, durable placebo response, possibly reflecting opicapone's clinical reputation heightening expectations, alongside the documented link between placebo exposure and striatal dopamine release in PD. They noted the magnitude of improvement in both arms exceeded typical expectations for a pharmacologic PD intervention, suggesting a ceiling effect limited detection of incremental benefit. Although the authors proposed opicapone as an option for wearing-off–associated pain based on numerical trends, that framing should be read cautiously given the trial did not meet its primary end point.

Limitations and Future Research

The study was not powered to detect off-time differences, and the population was not selected primarily on motor symptom severity. The COMT Val158Met polymorphism, linked to placebo responsiveness, was not evaluated, and greater tramadol use in the placebo group may have masked treatment differences. The authors called for designs that better control placebo response, excluding placebo responders during run-in, using wearable or AI-based objective pain monitoring, employing multiple pain scales with defined baselines, and shortening trial duration.

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REFERENCES
1. Chaudhuri KR, Ferreira JJ, Antonini A, et al. Challenges of Pain in Parkinson's Disease: Results from the OCEAN Study. Mov Disord. Published online June 8, 2026. doi:10.1002/mds.70390
2. Antonini A, Tinazzi M, Abbruzzese G, et al. Pain in Parkinson's disease: facts and uncertainties. Eur J Neurol. 2018;25(7):917-e69. doi:10.1111/ene.13624
3. Ferreira JJ, Lees A, Rocha JF, et al. Opicapone as an adjunct to levodopa in patients with Parkinson's disease and end-of-dose motor fluctuations: a randomised, double-blind, controlled trial. Lancet Neurol. 2016;15(2):154-165. doi:10.1016/S1474-4422(15)00336-1
4. Trenkwalder C, Chaudhuri KR, Martinez-Martin P, et al. Prolonged-release oxycodone-naloxone for treatment of severe pain in patients with Parkinson's disease (PANDA): a double-blind, randomised, placebo-controlled trial. Lancet Neurol. 2015;14(12):1161-1170. doi:10.1016/S1474-4422(15)00243-4
5. Iwaki H, Ando R, Tada S, et al. A double-blind, randomized controlled trial of duloxetine for pain in Parkinson's disease. J Neurol Sci. 2020;414:116833. doi:10.1016/j.jns.2020.116833